Treasure Coast Natives

At the suggestion of Virginia nature friend Pat Bowman, how about wild plants and hurricanes. Do the wild plants care?

Some relocate.  It seems that during Hurricane Wilma in 2005, a tropical weedy grass. Steinchisma laxum, previously unknown in North America invaded South Florida Florida arrival was overdue, an easy breezy hurricane hop from the Caribbean, assuming the hurricane did it.   Blog co-conspirator John Bradford standing in Halpatioke Park was the first soul in North America to say, “hey this does not fit the measurements of any grasses expected around here.”    Now you can hardly escape it.

Steinchisma laxum is everywhere, perhaps thanks to Wilma.

My lawn today still has on it millions of small leafy twigs shed from Live Oaks.  It is obvious to reckon, “well the gusts blew those free.”  True,  and  branches whipping wildly knocked them off too.  But there’s more to it than immediate physical damage.    That something more is cladoptosis, defined as “planned” twigdrop.   It happens in certain trees, notably in Oaks.

Earlier research indicates the tree somehow “decides” which twigs shall live and which shall shed.    Determination occurs early in the life of the twig.  Those fated to shed follow an odd development:  the “veins” connecting them to their parent branch narrow and choke off supply.   It looks like a ring of decay girdles the twig at the snap-off point, and the bark appears to pinch in.   When the twig separates, the severed base is not fractured and splintered, but rather more of a rounded knob, like your femur joining your pelvis, essentially “designed” to drop free smoothly.

Irma-severed end of Live Oak twig.  Unplugged cleanly, not torn, splintered, or fractured.

Why?  The limited literature indicates a hormonal seasonal reaction abetted by stress.  In short, those scattered twiglets were poised to come loose before Irma roared in.   The storm merely shortened the timeframe to hours instead of weeks or months.   The tree conceivably needs all its leaves during the moist growing season, but can’t support the full canopy as the warm wet season winds down and dry times approach.   The hormone ethylene is implicated.   The same hormone serves commercially to defoliate crops for easy harvest.  The twigdrop helps storm-proof the tree by reducing wind drag.  How many wind storms does a 500-year-old Live Oak experience?

Although Slash Pines may fracture or topple, another common probability is shedding, not little twigs, but rather large dead branches low on the trunk.  Ever notice how those trees have nice green canopies up high but not many dead branches down low?    There’s a perception that the branch-shedding is protection from ground fires, and that maybe those old branches even have some basal weakness to set them free.   “Cladoptosis” of large branches?   Maybe…more research needed.  The break-off is not clean, uniform, and mechanical as the Oak twigs.   Walking in The Haney Creek Natural Area today John and I saw the broken pine branches to be all sizes, alive, and dead, and torn and splintered.   Less  convincingly “preplanned” than Oak twiggies.

Pine branch shedding uneven, messy, and fractured.

Many woodland trees lie prostrate from past thunderstorms and hurricanes.   My favorites are in swamps:  Red Maples and Sweetbay Magnolias where the fallen tree resurrects multiplied as branches rise vertically to become new trunks.  Ex uno plures!  From one comes many, a whole new mini-population.

Busted-off branch bases and torn bark on standing tree trunks invite trouble and may or may not heal.    Healing comes mostly from above, which is why branch-stumps tend to fare poorly…”above” is gone.    Sugars, hormones, and growth processes cover a wound mostly downward, like pulling down a window shade.

After pruning, grazing, or hurricanes new stems grow from the lateral buds situated where the leaf joins a skinny young twig.   Repeat, skinny young twig.   But on any tree damaged in a storm  a few years ago new branches sprout from the thick old trunk.   How can that be, that gnarly old trunk lost its lateral buds decades ago.   Well, not entirely, that old bark has an amazing emergency repair mechanism known as latent buds.  Latent buds creep outward hidden within the bark as the tree expands, waiting for hurricane day.  The equivalent of me sprouting a new leg should one be yanked off.

Latent buds in bark competing to replace severed stem on Strangler Fig.

The magical regenerative powers of plants go doubly in an environment where storms and fires are endemic, such as here.  Check a wild area after a major storm, and there is likely less damage than expected, in some places no damage is even detectable.  That was almost true in Haney Creek today, Liatris all abloom, Hog Plums with plums still attached, and most foliage intact and green.  The native flora evolved to stand up to trouble.   And where destruction does occur, the ability of life to rise from subterranean structures or from broken plants is quick.    Moreover, the soil seed bank is ready to rise.   Disturbed dirt never stays bare for long.

If you want to find damage, seek it near the sea.  The salty winds “burn” foliage, and sow salt into the soggy earth.   The plants mostly recover ok from the saline attack.   Guess what species is especially resistant.  Live Oak.

Does a big hurricane change the composition of the flora?  Sure, within the constant ebb and flow of species in our dynamic world, but, given the fact that our flora has evolved through thousands of hurricanes, one event won’t cause radical mischief, except maybe where human activity has created an unnatural imbalance.

Upon emerging from our bunkers the morning the tempest subsided, one of the most positive sights after, “hey, we still have a fence,” were blue jays and butterflies.  Where did those jays ride out the fury, and a butterfly in a hurricane, well, that’s just poetic.

What a dumb time to write a South Florida blog, as we all wait for Hurricane Irma to blow in some new weed species.   After the house is as ready as possible,  there’s not much to do other than hang around and fret.   So, here’s something to read before the power blinks out.   Today’s core topic came from my second favorite thing after vanilla cream donuts, “This Week in Virology” by Professor Vincent Racaniello who makes all things viral fascinating.

Can a virus be good?  Yes, occasionally, and probably far more often than we know.  Today we shall see a native grass species (if you stretch the taxonomy) and its associated fungus meet a helpful virus.

Dichanthelium,  the Witch Grasses, comprise roughly 80 species,  numbering about a dozen in our usual neck of the woods.   Pretty, often petite, sometimes forming rosettes.

Dichanthelium chamaelonche.  All photos by John Bradford.

Today is all about a super-powered grass formerly classified as belonging to our local D. acuminatum.

D. acuminatum

Dichantheliums are notoriously tough to classify.  In any case the variants of interest are not known in Florida, but rather at scattered hot springs over a large area of western North America.    A recent and credible classification  interprets the hot-springs-inhabiting populations as a species in its own right, D. thermale.    A grass at home in hot water?    Really hot.

Recently studied in Yellowstone Park the witch powers of Witch Grass are proven where it bubbles bubbles toils and troubles in natural cauldrons as steamy as 65 degrees C (149 degrees Fahrenheit).  For comparison,  hot tap water is typically around 50 degrees C (122 degrees F).

The super-grass hosts a symbiotic fungus called Curvularia protuberata, at first glance a suspect responsible for the empowerment.  But infecting the grass with the fungus doesn’t help.   UNLESS a third player is tossed into the brew, not eye of newt, but a newly discovered virus.    The virus plus the fungus jointly confer heat resistance on the grass.

A big problem with symbiosis is that the codependent species must have coordinated reproduction and dispersal.    Our hotfoot grass turns up in small isolated populations at hot springs sprinkled over hundreds of miles.   Do the Three Musketeers all travel together?    How?  One component is known…the virus moves generation to generation in the fungus within the fungal clonal spores.   Then do those virus-bearing spores ride along somehow in the grass’s seeds?  Unknown, but don’t they have to?  How did the three species hop from Yellowstone to northern California and far beyond?

There may be more similar  fungal-viral-grassy unions to discover, because our fungal genus Curvularia is large, often plant-pathogenic, and frequently consorting with grasses.   The same fungal species in the Witch Grass, Curvularia protuberata, is also a pathogen on rice, so who knows, maybe it helps the rice sometimes?   And if in rice, it must infect additional grasses.  Could the empowering fungus-virus duo help concoct super-powered rice?

The mechanisms of all this are poorly known so far, but researchers understand a few things.  When the virus infects the fungus, the fungus accumulates mannitol, a sugar-alcohol common in plant defense mechanisms, and also a human medicine, such as a laxative.   Does the viral infection put the fungus into a defensive mannitol-making posture, and then the grass exploits the fungal protective arsenal?  Probably much more complicated than that simplistic first notion.

The grass, fungus, and virus have drawn the active attention of researchers interested in heat tolerant crops.  That’s a big deal in a world where hot conditions limit crop options, and where climate change will boost the mercury.  Experiments have already created heat-tolerant tomatoes by infecting them with the Dichanthelium fungus-virus sidekicks.

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Sesuvium portulacastrum

(Sesuvium references an ancient Gallic tribe.   Portulacastrum notes false similarity to Portulaca.)

Aizoaceae

A  romantic stroll on the beach in Florida or throughout much of the warm climate world may reveal a trailing succulent with showy purple-violet flowers. The fruit opens like the lid of a Weber Kettle to allow seeds to splash out, much like the pod of its namesake Portulaca.

Sea-Purslane sometimes goes by the name Sea-Pickle.  Plant munchers eat the salty succulent leaves.  Perhaps not a grand idea, however, as the tissues are powerful mercury (and probably lead) accumulators, not to mention producers of steroid hormones.   A few words on those:

Twenty-hydroxyecdysone is a steroid touted for boosting testosterone for virile body builders. I think the claim is spurious, and who wants to go around ingesting hormones?  If John and I become more manly we’ll be dangerous.

Photo by John Bradford.

Why would a plant make animal-active steroids?  Twenty-hydroxyecdysone is an insect molting hormone, serving to disrupt insect development, thus perhaps a future natural insecticide crop.

Insect damage to Sea-Purslane was the object of a hurricane recovery study in the Bahamas where hungry moth larvae undaunted by hormones stifled hurricane recovery by eating the pickles faster than they regrew.    What saved the day was a population of Brown Anole lizards, native in the Bahamas and introduced and established abundantly in Florida.  They had the fever for the flavor of a caterpillar.

It is always curious how plants of salty places cope with all the salt.   Some secrete it one way or another.   But Sea Purslane stores it!  Exposure to salt, in fact, up-regulates hundreds of known genes and enhances growth. The plants sequester extreme salt concentrations within the thick leaves, in the vacuoles to be exact.  A vacuole is sort of a bag inside a plant cell, and stashing the salt there may cut down its damage to basic cell functions.

The “purpose” of the stash however is not to place the salt out of harm’s way, but rather it seems using it in a “fight fire with fire” strategy.   The beach sand is highly salty of course, and that draws water out of the roots by osmosis.   You might say “salt sucks.”  People have long known that salt in the soil kills plants.   To smite the Sichemites, sow salt on their fields and dehydrate the crops.

Sea-Purslane fights salt with salt.   If a high soil salt concentration forces a tug-o-war for water, the way to win is to have even more sucky salt in the leaves.    A thick stand of Sea-Purslane can take up enough salt to diminish meaningfully the salt concentrations in the soil,  an observation not overlooked in soil reclamation.

Old World Diamond Flower (Oldenlandia corymbosa) Rubiaceae (Coffee Family)

Rustweed (Polypremum procumbens) Tetrachondraceae

John and trekked out to where the wild things grow today, only to retreat beat by the heat.   (Not John, I was the wimp.)  But not before a familiar observation:   clustering of similar yet unrelated flowers in a specific habitat.  A hunch rooted only shallowly in the botanical literature, so we’re in the realm of suspicion, not fact.  Maybe that heat got to my head.

Ever visit a natural place and perceive many unrelated flowers to look alike, especially in coloration?     A wet meadow may feature bright yellow xyris, bright yellow St. Johnsworts, bright yellow coreopsis, bright yellow heleniums, bright yellow smallfruit beggarsticks, bright yellow ludwigias, and more, although not to the exclusion of other colors.   Large white giant whitetops and large white alligator-lily grow together.  Where does imagination end and correlation begin?

Color clustering might be conceivable if you look at it this way:  pollination is essential for existence, so a plant is going to exist only where its proper pollinators are.   Different types of pollinators have different frequencies in different habitats, influencing the plant species composition, and thus perhaps trends in flower color and size.

Furthermore, and only a notion, maybe there is positive feedback, say, for example, a happy place for bumblebees brings bumble-visited flowers, which then draw more bumblebees, and these in turn support more bumblebee-o-centric flowers.   Bees like yellow.

This morning’s site, Haney Creek Natural Area in Jensen Beach, Florida, has a dry, sun-cooked, sterile, disturbed gravel road with a preponderance of very small white flowers.  “The same” road with essentially the same species runs behind my home, where almost all the flowers were about ¼ inch or less in diameter and white.   All of the photos today are taken in one small flower patch at the same magnification except for the over-magnified Buttonweed whose flowers are essentially the same size as the others.  Maybe that harsh habitat fosters tough little bees or mini-flies adapted to tiny white blossoms.

That harsh environment is probably not a place for plant species with big, showy, “expensive” flowers to support large insects demanding abundant rewards in nectar or pollen.    Skimpy man habitat, skimpy flowers, skimpy pollinators, perhaps.

Floral resemblance among the species growing intermixed there can be striking.  Below are photos of two unrelated plants:  native Rustweed (Polypremum procumbens) and non-native Old World Diamond Flower (Oldenlandia corymbosa).    Their flowers are “stamped from the same mold.”

Rustweed

Old World Diamond Flower

Non-native Buttonweed was growing among the others, and has much the same look.   This photo is at much higher magnification than the rest.

As an aside, Rustweed goes through a remarkable seasonal color change.    It starts out green and as the summer progresses switches to a coppery rusty color.

Rustweed in the rusty phase.

The other species consorting with the Rustweed and Diamondflower looked much the same too.   What makes the similarities even weirder is that the “flowers” are not all true flowers.  In the Canadian Horseweed they are a collection of smaller flowers collected into a white flower-head.   In the Sandmat and in the Euphorbia, the “petals” are itsy white leaves surrounding smaller flowers.  Yet they all have converged on the same general appearance, perhaps to accommodate the same floral visitors.

Boerhavia erecta, mixed with the others.  Not native.

Grassleaf Euphorbia, hanging with the others.   Not technically a flower,  but posing like one.   It is a cluster of small flowers associated with those small petal-like leaves. The big green lump is a fruit.

Sandmat, another non-flower disguised as a small white flower,  constructed similarly and related to the euphorbia immediately above.

And another in the “little white flower” patch. Canadian Horseweed.  The “flower” is a flower head made of many.

There must be something good about that “little white flower” look, because everyone on the berm is doing it.   And that good thing is probably shared pollinators.    Just a hunch.